326 lines
7.6 KiB
C
326 lines
7.6 KiB
C
/**
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*
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* \section COPYRIGHT
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*
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* Copyright 2013-2014 The libLTE Developers. See the
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* COPYRIGHT file at the top-level directory of this distribution.
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*
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* \section LICENSE
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*
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* This file is part of the libLTE library.
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*
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* libLTE is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation, either version 3 of
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* the License, or (at your option) any later version.
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*
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* libLTE is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* A copy of the GNU Lesser General Public License can be found in
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* the LICENSE file in the top-level directory of this distribution
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* and at http://www.gnu.org/licenses/.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <strings.h>
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#include <unistd.h>
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#include <math.h>
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#include <time.h>
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#include "lte.h"
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typedef _Complex float cf_t;
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int frame_length = 1000, nof_frames = 128;
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float ebno_db = 100.0;
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unsigned int seed = 0;
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bool tail_biting = false;
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int K = -1;
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#define SNR_POINTS 10
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#define SNR_MIN 0.0
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#define SNR_MAX 5.0
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#define NCODS 3
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#define NTYPES 1+NCODS
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void usage(char *prog) {
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printf("Usage: %s [nlestk]\n", prog);
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printf("\t-n nof_frames [Default %d]\n", nof_frames);
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printf("\t-l frame_length [Default %d]\n", frame_length);
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printf("\t-e ebno in dB [Default scan]\n");
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printf("\t-s seed [Default 0=time]\n");
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printf("\t-t tail_bitting [Default %s]\n", tail_biting ? "yes" : "no");
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printf("\t-k constraint length [Default both]\n", K);
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}
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void parse_args(int argc, char **argv) {
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int opt;
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while ((opt = getopt(argc, argv, "nlstek")) != -1) {
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switch (opt) {
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case 'n':
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nof_frames = atoi(argv[optind]);
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break;
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case 'l':
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frame_length = atoi(argv[optind]);
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break;
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case 'e':
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ebno_db = atof(argv[optind]);
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break;
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case 's':
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seed = atoi(argv[optind]);
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break;
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case 't':
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tail_biting = true;
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break;
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case 'k':
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K = atoi(argv[optind]);
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break;
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default:
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usage(argv[0]);
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exit(-1);
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}
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}
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}
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int main(int argc, char **argv) {
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int frame_cnt;
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float *llr;
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unsigned char *llr_c;
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char *data_tx, *data_rx[NTYPES], *symbols;
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int i, j;
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float var[SNR_POINTS], varunc[SNR_POINTS];
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int snr_points;
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float ber[NTYPES][SNR_POINTS];
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unsigned int errors[NTYPES];
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viterbi_type_t viterbi_type[NCODS];
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viterbi_t dec[NCODS];
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convcoder_t cod[NCODS];
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int coded_length[NCODS];
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int n, ncods, max_coded_length;
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parse_args(argc, argv);
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if (!seed) {
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seed = time(NULL);
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}
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srand(seed);
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switch (K) {
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case 9:
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cod[0].poly[0] = 0x1ed;
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cod[0].poly[1] = 0x19b;
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cod[0].poly[2] = 0x127;
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cod[0].tail_biting = false;
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cod[0].K = 9;
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viterbi_type[0] = viterbi_39;
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ncods=1;
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break;
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case 7:
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cod[0].poly[0] = 0x6D;
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cod[0].poly[1] = 0x4F;
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cod[0].poly[2] = 0x57;
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cod[0].K = 7;
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cod[0].tail_biting = tail_biting;
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viterbi_type[0] = viterbi_37;
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ncods=1;
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break;
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default:
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cod[0].poly[0] = 0x1ed;
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cod[0].poly[1] = 0x19b;
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cod[0].poly[2] = 0x127;
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cod[0].tail_biting = false;
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cod[0].K = 9;
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viterbi_type[0] = viterbi_39;
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cod[1].poly[0] = 0x6D;
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cod[1].poly[1] = 0x4F;
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cod[1].poly[2] = 0x57;
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cod[1].tail_biting = false;
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cod[1].K = 7;
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viterbi_type[1] = viterbi_37;
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cod[2].poly[0] = 0x6D;
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cod[2].poly[1] = 0x4F;
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cod[2].poly[2] = 0x57;
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cod[2].tail_biting = true;
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cod[2].K = 7;
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viterbi_type[2] = viterbi_37;
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ncods=3;
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}
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max_coded_length = 0;
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for (i=0;i<ncods;i++) {
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cod[i].R = 3;
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cod[i].framelength = frame_length;
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coded_length[i] = cod[i].R * (frame_length + ((cod[i].tail_biting) ? 0 : cod[i].K - 1));
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if (coded_length[i] > max_coded_length) {
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max_coded_length = coded_length[i];
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}
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viterbi_init(&dec[i], viterbi_type[i], cod[i].poly, frame_length, cod[i].tail_biting);
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printf("Convolutional Code 1/3 K=%d Tail bitting: %s\n", cod[i].K, cod[i].tail_biting ? "yes" : "no");
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}
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printf(" Frame length: %d\n", frame_length);
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if (ebno_db < 100.0) {
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printf(" EbNo: %.2f\n", ebno_db);
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}
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data_tx = malloc(frame_length * sizeof(char));
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if (!data_tx) {
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perror("malloc");
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exit(-1);
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}
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for (i = 0; i < NTYPES; i++) {
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data_rx[i] = malloc(frame_length * sizeof(char));
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if (!data_rx[i]) {
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perror("malloc");
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exit(-1);
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}
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}
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symbols = malloc(max_coded_length * sizeof(char));
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if (!symbols) {
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perror("malloc");
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exit(-1);
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}
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llr = malloc(max_coded_length * sizeof(float));
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if (!llr) {
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perror("malloc");
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exit(-1);
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}
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llr_c = malloc(2 * max_coded_length * sizeof(char));
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if (!llr_c) {
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perror("malloc");
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exit(-1);
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}
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float ebno_inc, esno_db;
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ebno_inc = (SNR_MAX - SNR_MIN) / SNR_POINTS;
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if (ebno_db == 100.0) {
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snr_points = SNR_POINTS;
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for (i = 0; i < snr_points; i++) {
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ebno_db = SNR_MIN + i * ebno_inc;
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esno_db = ebno_db + 10 * log10((double) 1 / 3);
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var[i] = sqrt(1 / (pow(10, esno_db / 10)));
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varunc[i] = sqrt(1 / (pow(10, ebno_db / 10)));
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}
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} else {
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esno_db = ebno_db + 10 * log10((double) 1 / 3);
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var[0] = sqrt(1 / (pow(10, esno_db / 10)));
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varunc[0] = sqrt(1 / (pow(10, ebno_db / 10)));
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snr_points = 1;
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}
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float Gain = 32;
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for (i = 0; i < snr_points; i++) {
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frame_cnt = 0;
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for (j = 0; j < NTYPES; j++) {
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errors[j] = 0;
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}
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while (frame_cnt < nof_frames) {
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/* generate data_tx */
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for (j = 0; j < frame_length; j++) {
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data_tx[j] = rand() % 2;
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}
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/* uncoded BER */
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for (j = 0; j < frame_length; j++) {
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llr[j] = data_tx[j] ? sqrt(2) : -sqrt(2);
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}
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ch_awgn_f(llr, llr, varunc[i], frame_length);
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for (j = 0; j < frame_length; j++) {
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data_rx[0][j] = llr[j] > 0 ? 1 : 0;
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}
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/* coded BER */
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for (n=0;n<ncods;n++) {
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convcoder_encode(&cod[n], data_tx, symbols);
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for (j = 0; j < coded_length[n]; j++) {
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llr[j] = symbols[j] ? sqrt(2) : -sqrt(2);
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}
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ch_awgn_f(llr, llr, var[i], coded_length[n]);
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vec_quant_fuc(llr, llr_c, Gain, 127.5, 255, coded_length[n]);
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/* decoder 1 */
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viterbi_decode_uc(&dec[n], llr_c, data_rx[1+n]);
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}
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/* check errors */
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for (j = 0; j < NTYPES; j++) {
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errors[j] += bit_diff(data_tx, data_rx[j], frame_length);
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}
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frame_cnt++;
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printf("Eb/No: %3.2f %10d/%d ",
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SNR_MIN + i * ebno_inc,frame_cnt,nof_frames);
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for (n=0;n<NTYPES;n++) {
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printf("BER: %.2e ",(float) errors[n] / (frame_cnt * frame_length));
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}
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printf("\r");
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}
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printf("\n");
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for (j = 0; j < NTYPES; j++) {
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ber[j][i] = (float) errors[j] / (frame_cnt * frame_length);
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}
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if (snr_points == 1) {
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printf("BER uncoded: %g\t%u errors\n",
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(float) errors[0] / (frame_cnt * frame_length), errors[0]);
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for (n=0;n<ncods;n++) {
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printf("BER K=%d: %g\t%u errors\n",cod[n].K,
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(float) errors[1+n] / (frame_cnt * frame_length), errors[1+n]);
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}
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}
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}
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if (snr_points > 1) {
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printf("\n");
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FILE *f = fopen("output.m", "w");
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if (!f) {
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perror("fopen");
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exit(-1);
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}
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fprintf(f, "ber=[");
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for (j = 0; j < NTYPES; j++) {
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for (i = 0; i < snr_points; i++) {
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fprintf(f, "%g ", ber[j][i]);
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}
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fprintf(f, "; ");
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}
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fprintf(f, "];\n");
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fprintf(f, "snr=linspace(%g,%g-%g/%d,%d);\n", SNR_MIN, SNR_MAX, SNR_MAX,
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snr_points, snr_points);
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fprintf(f, "semilogy(snr,ber,snr,0.5*erfc(sqrt(10.^(snr/10))));\n");
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fprintf(f, "legend('uncoded',");
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for (n=0;n<ncods;n++) {
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fprintf(f,"'1/3 K=%d%s',",cod[n].K,cod[n].tail_biting?" tb":"");
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}
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fprintf(f,"'theory-uncoded');");
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fprintf(f, "grid on;\n");
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fclose(f);
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}
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for (n=0;n<ncods;n++) {
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viterbi_free(&dec[n]);
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}
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free(data_tx);
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free(symbols);
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free(llr);
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for (i = 0; i < NTYPES; i++) {
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free(data_rx[i]);
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}
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printf("Done\n");
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exit(0);
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}
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